The B-WELL-Mom clinical centers, Northwestern University and the University of Alabama Birmingham, will recruit a total of 400 asthmatics (200 with well-controlled asthma and 200 with sub-optimal asthma control) and 150 women without asthma from their prenatal clinic populations. Asthma control assessment will be based on the criteria described in the NHLBI expert panel report. Except for asthma history questions, control subjects follow the same protocol. All patients will have four study clinic visits. At the first visit, all women will be offered a Thyroid-stimulating Hormone test and results will be reported to their care provider. At each visit, clinical assessments will include blood pressure, pulse oximetry, peak flow, FEV1 and FEV6. Biologic specimens will also be collected. Patients complete questionnaires related to symptoms and risk factors for exacerbation or mediation of asthma or breathing problems. Flow cytometry will be conducted to count immune cells including T-regulatory cells. All of the clinical data collection procedures are well-established procedures with minimal risk and the study surveys are based on preexisting, validated questionnaires. Between clinic visits, women will record their peak flow, exhaled nitric oxide and answer questions on symptoms, medications and other factors that might interfere with breathing. Medical record review will capture emergency visits and hospitalizations as well as details of labor and delivery.